Quantum-Enhanced Ephemeral State Orchestration for the A-scheme: The State-as-a-Certificate Paradigm and KSS-18 Optimization

This letter addresses a critical security-efficiency trade-off in the A-scheme: the vulnerability of static pairing-based public keys to quantum cryptanalysis versus the requirement for constant-size signature aggregation in Multi-Party Computation mode. We propose a hybrid architecture that encapsulates authentication within a symmetric hash-based state controller, formalizing the State-as-a-Certificate paradigm. By treating the public key as a transient derivative of the ephemeral protocol state, the framework achieves forward secrecy and facilitates zero-metadata steganographic transport. Furthermore, we demonstrate that this ephemeral orchestration resolves the Quantum-Assistance Paradox, enabling the safe scaling of the packing dimension $\eta$ to extreme ranges ($24 \leqslant \eta \leqslant 64$) by utilizing a quantum co-processor for legitimate decryption within the ECC paradigm. Analytical results show that transitioning to the Kachisa–Schaefer–Scott curves family, optimized via inverse isogeny mappings, provides a superior security margin against Shor's algorithm and lower computational overhead for point-to-uniform obfuscation compared to the Barreto–Lynn–Scott curve.